BigDecimal can't be coerced into BigDecimal

Question

This should be pretty simple, yet it's blowing up. Any ideas?

d = BigDecimal.new("2.0")
YAML::load({:a => d}.to_yaml)
TypeError: BigDecimal can't be coerced into BigDecimal
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `inspect'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `inspect'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `block in <module:IRB>'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:30:in `call'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:30:in `inspect_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/context.rb:260:in `inspect_last_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:311:in `output_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:160:in `block (2 levels) in eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:273:in `signal_status'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:156:in `block in eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:243:in `block (2 levels) in each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `loop'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `block in each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `catch'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:155:in `eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:70:in `block in start'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:69:in `catch'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:69:in `start'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/bin/irb:16:in `<main>'Maybe IRB bug!

Answer 1

This is a bug that has been reported and fixed.

The best solution would be upgrade to the latest Ruby (the fix is in patch level 194 onwards).

If you can’t upgrade your Ruby version, you can get the fix by installing the Psych gem. If you do this you’ll need to add gem 'psych' before you require 'yaml' (or add it to your Gemfile if you’re using Bundler) to load the code from the gem rather than from the standard library..